A conventional chair type massager includes a treating element that performs a back massage, a driving mechanism and the like in a backrest part. The conventional massager has been multi-functionalized by extending parts to be massaged from the back to other parts of a human body or including the functions of stretching the arms, legs, waist and other parts in addition to the function of massaging the back by the treating element.
For example, the conventional massager includes a plurality of air bags holding arms or legs so that the parts of a human body to be treated, such as the back and other parts, can be restricted from moving. In this state, a mechanical massage performed by the treating elements is combined with a massage performed by the air bags or with a raising/tilting operation (reclining operation) of the backrest part, thereby performing more effective massage or stretch. (see, e.g., Japanese Patent Laid-Open Application Nos. 2005-013463 and 2005-152260).
The massagers of the aforementioned JP-A-2005-013463 and JP-A-2005-152260, however, have following problems, when the arm stretch is performed. These massagers have air bags in armrest parts in which arms are inserted. As air is supplied into the air bags, arms are fixedly held by the swelled air bags, and the arm stretch is performed by tilting a backrest part. However, it takes a predetermined time to tilt the backrest part backward until a user feels that the arms are stretched. If the air is continuously supplied to the air bags to hold the arms while the predetermined time passes, the bloodstreams of the arms are obstructed so that the arms become tired and the massage feeling gets worse.
To avoid such an excessive air supply described above, a pressure retaining valve (to be described later) that maintains air within the air bags at a constant level can be used to control the pressure applied to the arm at a specific level. However, in such a case, a space is required for installing the pressure retaining valve. Moreover, since the pressure retaining valve is expensive compared to the simple opening/closing valve, this causes an additional cost. The pressure retaining valve is a valve such as a back pressure valve or a primary pressure regulating valve. If pressure is higher than the predetermined pressure, the pressure retaining valve releases extra pressure and maintains the pressure at a specific level before entering through the pressure retaining valve. That is, the pressure retaining valve maintains a secondary pressure so as to be constant, by releasing the primary pressure. In addition, the pressure retaining valve is distinguished from a pressure reducing valve.